In the era of electronic data access, businesses and organizations rely heavily on instant access to centralized data storage systems. These systems store vast amounts of data that are easily searchable and can be readily processed to produce documents for internal or external use. Due to the electronic nature of these data storage systems, around-the-clock access is not only assumed possible, but is paramount to the success of businesses and organizations relying on the data. A loss in ability to access data stored in the data storage system often forces the business to temporarily pause its operation causing a loss in revenue and customers.
Data storage systems are typically one or more data storage devices which store data coupled to a processing unit for accessing and processing the stored data. The data storage devices can include tape drives, hard drives, solid-state devices, or any other memory. Data stored on the data storage device are organized into data sets according to the system designer's specifications. Clients access the data storage system through terminals coupled to the data storage system.
Even during normal operation of a data storage system there may be a need to move (“migrate”) data sets from one location to another. The data sets may be moved to a different position on the same data storage device or moved to a new data storage device. For example, the data sets may grow in size and reach a capacity limit of a current data storage device. In such a case, the business will install a new larger capacity data storage device. The data sets will then need to be moved from the old device to the new device. Performing the move is preferably done without terminating client access to the data. Migration processes perform the move process.
The conventional migration processes typically execute in two steps: a mirror phase and a re-direction phase. During the mirror phase, data sets are copied from the old data storage device to a new data storage device and all subsequent updates to the data sets are mirrored to both data storage devices. At a time when the old and new storage devices are synchronized, the migration process enters the re-direction phase. During re-direction the clients are directed to access the new data storage device rather than the old data storage device. Re-direction ends and the migration process is complete after all open data sets are closed.
A challenge for migration processes is that the data is typically being accessed and modified by a client during the migration. As a result, the migration process must keep track of changes in the old data set and mirror those changes to the new data set. Due to the size of the data sets, migration can often take several days and the task of mirroring the old data set further delays the migration process from completing until access to the data set has terminated. A data set open 24 hours a day and 7 days a week leads to a never ending migration process.
One current solution to the problem involves shutting down all clients of the data storage system, completing the migration process, and then reconnecting with clients. Another known solution to the problem is an “OPEN” interface such that the client closes the old data set and reopens the new data set.
Disadvantages to these solutions include coordinating a shut down of all clients using the data sets in the migration process, which is complicated and interrupts ongoing operation. The migration process cannot complete until all open instances are closed, and while the data sets are closed the clients cannot operate.
Therefore, there is a need for migrating data sets without needing to close the data sets before completing the migration process.